Electrical control apparatus for heating plants



Aug. 29, 1939. P.HARTMANN-RIIS 2,171,099-

ELECTRICAL CONTROL APPARATUS FOR HEATING PLANTS Filed Feb. 15, 19:57

L P. Mar/6, m 7?! is Patented Aug. 29, 1939 UNlTED 'STATESQ' PATENT OFFICE ELEOTR ICAL CONTROL APPARATUS FOR HEATING PLANTS Petter Hartman- Kilo, Ostre Aker, near Oslo, Norway Application February 15, 1931, Serial No. 125,870 'In Norway February 14, 1936 3"Claims.

(Granted under the provisions or sec. 14, act of March 2, 1921;, o. q. 5)

will be entirely extinguished. When the 'tempcr-' ature has declined to a certain point the current circuit again will be closed, the motor starts and a full flame will again be established.

Thiscomplete and frequent extinctions and ignitions to complete flame have considerable drawbacks, as each ignition will cause a considerable amount of atomised oil-air-mixture to be blown into the fire box before ignition takes place, and which therefore will not be utilised and the temperature of the exit gases will be high, as the burner, when burning, always has a complete flame. Furthermore the working of the plant will be irregular, owing to the irregular heat supply. It has previously been suggested to obtain a completely regular working of an oil fired plant by varying the size of the flame in accordance with the momentary heat requirement.

Thus it is known to let the oil be drawn into the burner by the inflowing air, the quantity of which oil supply is controlled by a damper, the opening of which is controlled by a temperature influenced organ. However, this aspiration of the oil to the burner by the'air has several draw- ,1

of motor and thereby the size of the flame is controlled by connecting in series' two or more tem-- perature responsive switches, one, of which has an operative range which covers the range of all the others 'or the apparatus may consist of, only one switch with stagewise control. In case of several switches, onehas an operative range, of such scope as to embrace the operative range of the other switch or switches, The

-, ments of the invention are shown for regulating tively to-the burner, are driven by a common motor. According to the invention the velocity.

switch or switches with the intermediate operative ranges are connected in parallel with re- I sistances, in which the current flows when the switch is disconnected, while the switch with the widest operative range either is completely dis-' 5 connected 'or connected with or without resistance connected in series.

- In case of only one switch forthe stagewise control, the motor current in one of the stages passes through the.switch without resistance, 0

while in the other stages passing through one or more resistances connected in series with the switch. v

In the accompanying drawing several embodithe temperature or pressure of steam or hot water boilers.

- Fig. 1 shows diagrammatically the apparatus with two switches for regulation in two steps.

Fig. 2 shows the apparatus with one switch for regulation in two steps;

Fig. 3 illustratesapparatus with two switches for regulation in three steps and Fig. 4 shows a device similar to Fig. 1, in which a transformator is used for the voltage regulation.

In Fig. 1, I is the motor which drives the pump and the fan for passing oil and air to the burner, 2 and 3 are switches, which here are shown as the mercury type operated by thermoo stats and l is an adjustable resistance connected in parallelv with the switch 3. The circuit is clearly shownin the figure. The thermostat operating the switch 2 is adjusted to have an operative range between 40 and 50 centigrade, or interruption will take place at 50 and connection again established at 40, while the thermostat operating the, switch 3 has an operative range between 41' and 43 centrigrade. When the temperature in the .boiler rises, the 'switch 3 will open the circuit l6 at 43, but the current will not be interrupted, as it flows through thckresistance 4 whereby the current, the number of revolutions of the motor and the size of the flame decrease.

The size of the reduced flame may be controlled by adjusting the resistance 4. However, the temperature of the water in the boiler continues to rise owing to the radiance from the masonry below the boiler, even if the size of the flame has decreased. If the temperature increases for example to 47 and then decreases'the switch 3 will close the circuit l6 at 41 which results in a complete flame and increasing temperature. If, .on the other hand, the temperature increases to 50, then the switch 2 will open the circuit it and the flame will be extinguished. If the temoccur when the operative ranges of the two switches 2. and 3 and the size of resistance i are adequately adjusted.

Fig. 2 shows apparatus, with which the same effect is obtained as with the apparatus shown in Fig. 1 with only one temperature responsive switch. As will be seen, the thermostat operated switch here has three lines 5, ii, 1. With the position shown in Figure 2 the current passes through lines 5 and 6 without passing through any resistance, but when the mercury level has the position shown in dotted lines or the 4l5 centigrade position the current passes through the resistance 3 and the current declines. At 50f. the thermostat operated switch becomes wholly inactive and will move to the position, shown in Fig. 2 when the temperature has declined to 40.

Fig. 3 shows a combination of the arrangement shown in Figs, 1 and 2 with two temperature responsive switches, in which the flame is regulated in three steps. The switch 3@ is here the same as 3 in Fig. 1, while the thermostat of switch 26.

:is the same as in Fig. 2. When the switch 3t responds, at 43, the circuit will be closed over the resistance 41, and thereby the size of the flame will decline as described in connection with Fig. 1. By continued rise of the temperature, for example at 45 the resistance 5Q will become part of the circuit, and at 50 the current will be cut off by the switch it. During cooling the switch to will close at 41, but the circuit will be closed without including resistances, since the switch 2d also returns to its initial position, at 40.

It is clearly understood that the requisite number of regulation steps may be acquired by an adequate choice of thermostats or switches and their number.

Fig. 4 shows as an example how the voltage regulation may be efiected, by connecting the motor circuit across difierent voltage types of ti. secondary winding of a transformer it. The switch at in responding will be completely turned over, thereby connecting the lower voltage of the is of fundamental importance in carrying out theobjects of the invention and changes in adjustment of the switches and the consequent temperatures at which the switches operate may be varied without departing from the spirit and scope of the invention as long as the hereinabove described steps or sequence is maintained.

I claim:

1. Apparatus for automatically controlling the heat output of an oil fired heating plant having the oil supplied thereto by a pump and a fan driven by a single motor comprising an electrical supply circuit having one side thereof connected to one terminal of the motor, a circuit extending from the other motor terminal adapted to be connected to the other side of the supply line,

voltage limiting means associated with said second mentioned circuit, a thermo-responsive switch adapted to connect said second mentioned circuit to said supply circuit when a predetermined low temperature is reached and open said circuit when a predetermined maximum temperature is obtained from the heating plant, a second theme-responsive switch associated with the motor circuit having an operable range inter- 'mediate of the operable range of the first mentioned switch, and said second mentioned switch being operable to connect said voltage limiting means in the motor circuit when a predetermined is obtained from the intermediate temperature heating plant.

2. Apparatus for automatically controlling the heat output of an oil fired heating plant having the oil supplied thereto by a pump and a fan driven by a single motor comprising, an electrical supply circuit having one side thereof connected to one terminal of the motor, a circuit extending from the other motor terminal adapted to be connected to the other side of the supply line, voltage limiting means associated with said second mentioned circuit, two thermostatically operated switches associated with said second mentioned circuit, one of said switches being adapted to open and close at temperatures which are rebeing adapted to close the motor circuit across the supply line and open the same, and said switch having the intermediate range being operable to include said voltage limiting means in the motor circuit when the heat output of the plant has reached an intermediate predetermined temperature. Y

3. In apparatus for automatically controlling, the heat output of an oil firing heating plant having the oil supplied thereto by a pump and afan driven by a motor comprising,-an electrical supply circuit, voltage limiting means, a switch operably responsive to a predetermined low temperature for connecting said motor across the supply circuit, a second switch operably responsive to a temperature higher than said predetermined low for impressing a lower, voltage across said motor, said first mentioned switch being operable to disconnect said motor from the supply circuit at a predetermined maximum temperature, andw.

' said second mentioned switch b ing operable at a temperature slightly higher than said predetermined low temperature for eliminating the voltage limiting means whereby the motor will start on .full line voltage when said first mentioned switch reaches said predetermined low temperature. f 5 PEI'I'ER HAR'I'MANN-RIIS. 

